Crimp reservation process

ABSTRACT

There is disclosed a process for reserving and redeveloping crimp involving removing the crimp from self-crimped composite fibers, which originally developed their crimp under rather severe temperature or humidity conditions or both, then processing the decrimped fiber to the desired end product and finally redeveloping the original crimp by mild processing conditions.

United States Patent 1151 3,671,619

Fitzgerald et al. 1 June 20, 1972 541 CRIMP RESERVATION PROCESS [56] References Cited [72] lnventors: Warren E. Fitzgerald; John P. Knudsen, UNlTED STATES PATENTS bmh Raleigh; Jessie Cary 2.439.815 4/1948 Sisson ..264/DlG. 26 3.111.366 11 1963 Fujita et al. ..264/l82 x [73] Assignee: Monsanto Company, St, Louis, Mo, 3,242,243 3/]966 Knudsen ..264/78 3.330.895 7 1967 Fujita et al... ...264 103 ml March 3.038.237 6/1962 Taylor ..264/l82 3.038.240 6/ 1 962 Kovarik ..264/1 s2 L650 3.397.426 8/1968 Fujita et al ..264/2l0 F x Related US. Application Data Pnmary Examiner-Jay H. W00 Continuation-impart 0f SE1. 4 D AtI0rney-A. Milton ComwelLJr. and Russell E. Weinkauf 1963, abandoned.

[57] ABSTRACT [52] U.S.Cl ..264/l68,28/72.l7,161/173, There is disclosed a process for reserving and redeveloping 264/171 264/182 264/342 264/346 crimp involving removing the crimp from self-crimped com- [Sl] Int-Cl. ..D0ld 5/22 posite fibers which originally devehped their crimp under Field of seal'di 171,345; rather severe temperature or humidity conditions or both, 161/173; 28/72.]7 then processing the decrimped fiber to the desired end product and finally redeveloping the original crimp by mild processing conditions.

8 Claims, 3 Drawing Figures COMPOSITE CRlMPED F IBER HOT STRETCH TO REMOVE CRIMP COOL UNDER TENSION TO SET IN UNCRIMPED STATE PRQCESS TO YARN OR FABRIC PATENTEDJUN20 m2 COMPOSITE CRIMPED FIBER i-l oT S l'kE TCH 2 REMOVE CRIMP ZTENSION TO SET IN g-iUNCRIMPED STATE INVENTORS WARREN E. FITZGERALD JOHN P KNUDSEN JESSIE O. BROOK BY M! ATTORNEY CRIMP RESERVATION PROCESS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 331,890, filed Dec. 19, 1963, now abandoned.

BACKGROUND OF THE INVENTION A variety of methods have been developed and used to produce crimped synthetic filaments and fibers. Crimp in textile fibers imparts an aesthetic feel or hand to fabrics knitted or woven. In addition, covering power is improved by the bulk inherent in crimped fibers. One suitable method of imparting crimp involves the conjugate spinning of two or more difierent synthetic compositions together so that they form a unitary filament which contains the components in an eccentric relation over the cross section of the filament. When the components are properly selected, the filaments have the inherent ability to develop crimp under suitable conditions.

It is well established that drastic or severe conditions are required to develop crimp. In addition to crimping, these conditions also impart excessive shrinkage, which is degradative to structure dimensions, and under these conditions fabric or other structural restraints can sometimes inhibit crimp development.

If such fibers or filaments are processed to yarn or fabrics prior to crimp development, the crimp, which is desirable, can only be achieved by subjecting the yarn or fabric to relaxation conditions which in many instances are degradative to the dimensions or structure of the fabric. In many cases the conditions necessary for proper crimping are not readily applied to various fabrics and other shaped articles.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a process for reserving crimp in self-crimping composite fibers which originally had their crimp developed under extreme conditions in a reasonably tension free condition.

An additional object is to provide yams, fabrics and other shaped articles formed from fiber which has its crimp reserved and is capable of redeveloping its crimp under mild conditions in the shaped article.

A further object is to provide yarns, fabrics and other shaped articles formed from fiber which has its crimp reserved and redeveloped under mild conditions while in yarn, fabric or shaped article form.

An additional object of the invention is to provide a process for reserving crimp in self-crimping composite fibers which process follows the normal crimp development process of developing the desired crimp in the self crimping composite fiber while only loosely restrained in a relaxing environment, which process reduced the crimp amplitude by stretching the fiber under hot conditions which are milder than the relaxing conditions of the original crimp development and cooling the fiber under tension to set the fiber in the decrimped configuration achieved by the tension.

In general, the objects of the invention are attained by subjecting a self-crimped composite fiber which already has undergone a relaxing step under minimal restraints to develop the crimp level best suited to the intended end use; to a series of processing steps in which the crimp amplitude is reduced by stretching under hot conditions milder than the original crimp development conditions; the straightened fiber cooled to set the straightened form; the fiber processed to the desired end product; and the crimp amplitude redeveloped under mild processing conditions;

description of the drawing To further elucidate the invention, reference will be made to the attached drawing that forms part of the application.

In the drawing,

FIG. I is a flow sheet illustrating the manipulative steps used in carrying out the process of the invention;

FIG. 2 is a reproduction of a photomicrograph at a magnification of about I35 times of yarn made from a composite fiber of copolymers of acrylonitrile-vinyl acetate, 94:6 ratio, and acrylonitrile-vinyl acetate-styrene, 86. 4:9. 6:4. 0 ratio after stretching and before boiling water exposure;

FIG. 3 is a reproduction of the same yam as in FIG. 2 after exposure to boiling water.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS Prior to the operation of the process of this invention the composite fiber is' processed to the crimp level desired for any particular end use. This crimp level is attained by subjecting the composite fiber to crimp development conditions more severe than those the product will actually meet in end uses. Crimp development may be attained by means of a relaxing environment which may involve any one of several processing conditions well known in the prior art. For instance, the relaxing environment may conveniently consist of an annealing chamber in which the fiber is allowed to approach, substantially free of tension, an equilibrium conformation in which any remaining strains are self-compensated. The annealing chamber may contain hot air, or saturated steam at a pressure of from 5 to 50 psig. Alternatively, the tow or filament yarn may be continuously relaxed by steam or dry heat using any apparatus which permits shrinkage under little or no tension.

The first step of this invention is the reduction in crimp amplitude. The crimp amplitude is reduced bystretching the fiber under hot conditions by an amount sufficient to substantially straighten the fiber, but not sufficient to reduce the denier of the filaments by more than 30 percent. A change of denier indicates that the fiber itself is actually being stretched rather than just straightened. and should be avoided unless shrinkage as well as crimp potential of the fiber is desirable. Depending upon the type of composite fiber, the stretching operation may preferably involve stretches of from around 1. 05X to 4. 5X or greater. The conditions under which the stretching takes place preferably involve hot air, boiling water, or steam at a temperature above the softening temperature of the composite fiber in the medium employed. But in any case stretching should take place at a temperature less than that used for the original crimp development but greater than the softening temperature with the realization that such things as presence of water or plasticizing agents can effectively reduce the softening temperature. Such temperature conditions will, or course, vary considerably with the stretch medium and type of composite fiber being processed.

For the purposes of this invention, the softening temperature can be approximated by the temperature at which the uncrimped fiber exceeds 2. 0 percent elongation when heated, in an environment similar to the one in which the fiber is to be stretched, under a load of 0. l0 gr/denier at a uniform rate of temperature rise of 2 C. per minute. It will be recognized, however, that under certain circumstances, direct measurement of softening temperature under the actual stretch conditions selected may be quite difficult. In such cases it may be necessary to experimentally determine satisfactory operating conditions without the guidance of a predetermined softening temperature. In these circumstances operability must be the guiding criteria and failure to demonstrate a clear cut softening temperature should not be taken as limiting the practice of this invention.

After removal of the crimp amplitude, the composite fiber is subjected to cooling while under sufficient tension to maintain the essentially straight configuration to freeze in or "set" the fiber in the desired form. This involves cooling the fiber below its softening temperature so that the fiber will set and maintain the shape in which it has been placed by the hot stretching operation. In some cases the fiber, after cooling, may be given a light mechanical crimp to improve the processability of the product on textile equipment.

While it is possible, under certain circumstances, to remove crimp by stretching at temperatures below the softening temperature, such a process usually involves introduction of nonrecoverable distortions and cannot include the setting step which provides the dimensional stability prior to relaxation inherent in fibers processed according to this invention.

The composite fiber, having been set as indicated above, may be processed to yarn and/or fabric or other shaped articles as desired, such processing being easily accomplished since the fiber is not excessively bulked or entangled at the time of its being processed to the shaped article. However, no yarn processing step should involve temperatures above the softening temperature of the fiber if the crimp is to be further reserved. 1

After the composite fiber has been processed to the finished article, the crimp amplitude may be redeveloped by using relativelyv mild conditions and at this point will be permanent and elastic when subjected to distortion forces. The crimp recovery forces within the fibers are high enough that when the distorting influence is removed, the fiber can easily overcome small environmental restraints to achieve its original configuration. By this method, unrestrained filaments will recover at least 95 percent of the original crimp level imparted before the composite fiber was stretched. Filaments incorporated into yarns and/or fabrics may undergo slightly lower crimp recovery as a result of restraints imposed by yarn or fabric geometry. Crimp levels of to 25 crimps per extended inch of fiber are desirable and easily attained by this method. This presents a major improvement over previous methods of crimp development wherein the composite fiber was processed to the final shaped article and the crimp then developed either by very drastic treatment or under conditions which require special handling or construction of the fabric to develop bulk because of very low crimping forces.

The process of this invention may be operated in a continuous manner with very little time interval between the various steps before the fiber is processed to the finished article. However, if desirable, each step may be performed separately to allow for other fiber treatments such as the application of finishes, dyes'and the like.

The process of this invention is applicable to composite synthetic fibers that are self-crimping. The use of the term composite fiber" is intended to refer to a fiber comprising at least two different components of synthetic polymeric compositions with the components being eccentrically disposed toward each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other.

Especially suitable self-crimping composite fibers which may be subjected to the process of the invention include composite fibers wherein the components are comprised of acrylonitrile containing fiber-forming polymers. These acrylonitrile polymers which may be used for one or both components of the composite fiber include acrylonitrilepolymers such as polyacrylonitrile, copolymers and terpolymers of acrylonitrile and blends of polyacrylonitrile and copolymers of acrylonitrile with other polymerizable monoolefinic monomers as well as blends of polyacrylonitrile and such copolymers with small amounts of other polymeric materials such as polystyrene. In general, the polymer made from a monomeric mixture of which acrylonitrile is at least 70 percent by weight of the polymerizable content is useful in the practice of the present invention. Besides polyacrylonitrile, useful copolymers are those of 80 or more percent acrylonitrile and l or more percent of other mono-olefinic monomers. Block and graft copolymers of the same general type are within the purview of the invention. Suitable monoolefinic monomers include vinyl acetate and other vinyl esters of carboxylic acids, vinylidene chloride, and other vinylidene halides, vinyl chloride, vinyl bromide and other vinyl halides, dimethyl fumarate and other dialkyl esters of fumaric acid, dimethyl maleate and other dialkyl esters of maleic acid, methyl acrylate and other alkyl esters of acrylic acid, styrene and other vinyl-substituted aromatic hydrocarbons, methyl methacrylate, and other alkyl esters of methacrylic acid, vinylsubstituted heterocyclic nitrogen ring compounds such as vinylimidazoles, etc., the alkyl-substituted vinylpyridines, vinyl chloroacetate, allyl chloroacetate, methallyl chloroacetate, allyl glycidyl ether, methallyl glycidyl ether, allyl glycidyl phthalate and the corresponding esters of other aliphatic and aromatic dicarboxylic acids, glycidyl acrylate and other mono-olefinic monomers copolymerizable with acrylonitrile. Also suitable for use in this invention are blends formed of polyacrylonitrile or a copolymer of more than 90 percent acrylonitrile and up to 10 percent vinyl acetate and a copolymer of vinylpyridine or alkyl-substituted vinylpyridine and acrylonitrile, the said acrylonitrile being present in sufficient proportions to provide heat and solvent resistance in a substantial proportion of the vinylpyridine or derivative thereof to render the blend receptive to acid dyestuffs.

Preferably bicomponent compositions are those where one component is a copolymer containing to 95 percent by weight of acrylonitrile and 5 to 15 percent vinyl acetate and a second component which may also be a copolymer of acrylonitrile and vinyl acetate differing in the percent vinyl acetate, for example, from 0.5 to 5 percent difierence or a copolymer of at least 80 percent by weight of acrylonitrile,

and up to 20 percent of styrene or a terpolymer of at least 80 percent by weight of acrylonitrile, from 5 to 15 percent vinyl acetate and l to 7 percent vinyl bromide. Other especially useful combinations include those where one component is a terpolymer of acrylonitrile, vinyl acetate and R wherein R is a dye receptor such as cinnamic acid, itaconic acid or an olefinic sulfonate type receptor such as potassium vinyl benzene sulfonate, sodium vinyloxy-benzene sulfonate, or allyl p-toluene sulfonate and the other component is a polymer containing acrylonitrile, vinyl acetate, R and X wherein X is a copolymerizable monomer such as styrene, vinylidene chloride, vinyl bromide, an acrylate, or any other monomer previously mentioned.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 Polymers of acrylonitrile-vinyl acetate (AN-VA), 94:6 ratio, and acrylonitrile-vinyl acetate-styrene (AN-VA-S), 92:6:2 ratio, respectively, were cospun from a conjugate jet in a 1:1 ratio. The fiber had a softening temperature in water of 80 C. The fiber free of tension was exposed to high pressure (35 psig) steam for five minutes to develop crimp. The crimp level was about 35 crimps per extended inch of fiber. The fiber was tensioned at room temperature until the crimp amplitude was almost gone, then stretched 1.05 times in a boiling water bath and cooled at this extension. The fiber was processed through a stuffing box crimper maintained at room temperature. Six mechanical crimps per inch of fiber were obtained in the stuffing box.

The fiber was then cut to 2 b inches staple and processed into yarn by the cotton system. The yarn was knit into jersey and sweater constructions. The fabric produced underwent a bulking action when exposed to boiling water. Inspection of the yarn in these fabrics revealed that the filaments in the yarn had redeveloped their crimp and the yarns had become bulkier. The fabrics underwent only minor dimensional changes in the process of developing bulk.

EXAMPLE ll A composite fiber was produced by cospinning in a 1:l ratio a polymer of acrylonitrile-vinyl acetate (AN'VA), 94:6 ratio, and a polymer of acrylonitrile-vinyl acetate-styrene (AN-VA- S), :6:4 ratio, using a plate mixer standard spinnerette combination of the type disclosed in U.S. Pat. No. 3,295,552 by Powell et al. The fiber was piddled into a container which was placed in a high pressure (35 psig) steam chamber to develop crimp. The crimp level developed was about 25 crimps per extended inch of fiber. The crimped fiber was stretched 1. 3X in a boiling water bath and cooled at this elongation. The fiber was then given a light mechanical crimp via a stuffing box at room temperature to aid in further processing of the fiber. The fiber was cut to 2 k inches staple and processed into yarns by the cotton yarn system. The yarn when placed in boiling water bulked into a much larger diameter yarn as shown by P16. 2 and FIG. 3, which are reproductions of photomicrographs, at a magnification of 135X, of the yarn before and after placing in boiling water to redevelop crimp amplitude.

EXAMPLE III A composite fiber produced by cospinning, in a 3:1 ratio, an AN-VA(94:6) polymer and an AN-VA-vinylidene chloride (85. 2:8. :6. 8) polymer was cycled between atmospheric pressure and saturated steam at 35 psig for seven cycles. A crimp level of about l2 crimps per extended inch was developed. The crimped yarn was stretched 1. 2X in boiling water and quenched at this elongation. On reboiling without tension the fiber recovered the original crimp level.

EXAMPLE IV The polymer pair of Example I was spun and crimped as in Example ll and the fiber developed 15 crimps per extended inch.

The crimped fiber was stretched l. 1X in hot air at 185 C. and was cooled under tension. When the sample was reheated at the 185 C. free of tension, it redeveloped about 95 percent of its original crimp amplitude.

EXAMPLE V Polymers of AN-VA 94-6) and AN-S(88-l2) were cospun l :1 ratio) from a conjugate jet. The fiber had a softening temperature in water of 66 C. A sample was crimped in hot air at l45 C. free of tension and developed 40 crimps per extended inch. The crimp was removed by stretching 1. 2X in boiling water and cooling under tension. A sample of the fiber was placed free of tension in boiling water and redeveloped substantially all of the crimp amplitude.

EXAMPLE VI A composite fiber was prepared by cospinning in a lzl ratio a polymer of acrylonitrile-vinyl acetate (AN-VA), 93:7 ratio, and a polymer of acrylonitrile-vinyl acetate, 91. 5: 8. 5 ratio, using a plate mixer standard spinnerette combination of the type disclosed in U.S. application Ser. No. 425,491, by Powell et al. The fiber was piddled into a container which was placed in a high pressure (35 psig) steam chamber to develop crimp. The crimp level developed was about 22 crimps per extended inch of fiber. The crimped fiber was stretched l. X in water at 95 C. and cooled at this elongation. On boiling in water without tension the fiber recovered the original crimp level. A sample of the same fiber which had not been crimped in high pressure steam was also placed in boiling water. It developed essentially no self-crimp.

The crimp reservation process of this invention provides a practical method for obtaining self-textured, high bulk crimped) yarn or fabrics without the problems encountered in trying to process an already bulked fiber to yarn or fabric form. Using this process the fabric is prepared with the crimp fixed temporarily in the straight form (reserved crimp) and then the crimp is redeveloped after the fabric is complete. Thus, the reserved crimp fiber can beprocessed into yarn or fabric and retain the ability to redevelop crimp when heated, in a hot dye-bath, for example. The crimp-redevelopment forces are considerably higher than the yarn constraints, which will not reduce the crimp frequency already determined in the earlier crimp-development process. The most that fabric or yarn constraints will do is to reduce the crimp amplitude.

The foregoing detailed description has been given for clearness of understanding only, and unnecessary limitations are not to be construed therefrom. The invention is not to be limited to the exact details shown and described since obvious modifications will occur to those skilled in the art, and any departure from the description herein that conforms to the present invention is intended to be included within the scope of the claims.

We claim:

1. In the process for reserving and redeveloping crimp in self-crimping composite fibers from acrylonitrile polymers which have been subjected to the action of a relaxing environment comprising steam at 5 to 50 psig while substantially free of tension to impart crimp thereto, the improvement comprising the steps of (A) removing the crimp by stretching the fiber at a temperature above its softening temperature and below that of the relaxing environment, (B) cooling the fiber under tension to set the fiber in the configuration achieved by the tension, (C) processing the fiber to its final form and (D) redeveloping the fiber crimp by subjecting the fiber to temperatures and moisture conditions of not greater than about those of boiling water.

2. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of from 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate and a second polymeric component consisting of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate with a difference of from 0.5 to 5 percent vinyl acetate in the two components.

3. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate and a second component consisting of at least percent arylonitrile, up to l5 percent vinyl acetate and from 1 to 10 percent of an acrylate.

4. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of to percent acrylonitrile and 5 to 15 percent vinyl acetate.

5. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a terpolymer of 78 to 94 percent acrylonitrile, 5 to 15 percent vinyl acetate and l to 7 percent vinyl bromide and a second component consisting of at least 80 percent acrylonitrile, up to 15 percent vinyl acetate and 1 to 7 percent vinyl bromide.

6. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of from 85 to 95 percent acrylonitrile and from 5 to 15 percent vinyl acetate and a second polymeric component consisting of a terpolymer of 80 to 95 percent acrylonitrile, 5 to [5 percent vinyl acetate and 0.] to 5 percent of a copolymerizable sulfonate with a difference of from 0.5 to 5 percent vinyl acetate in the two components.

7. The process of claim 1 wherein the stretching is done in an atmosphere of boiling water.

8. The process of claim 1 wherein the stretching is from 15 to 350 percent. 

2. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of from 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate and a second polymeric component consisting of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate with a difference of from 0.5 to 5 percent vinyl acetate in the two components.
 3. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate and a second component consisting of at least 80 percent arylonitrile, up to 15 percent vinyl acetate and from 1 to 10 percent of an acrylate.
 4. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate.
 5. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric compoNent consisting of a terpolymer of 78 to 94 percent acrylonitrile, 5 to 15 percent vinyl acetate and 1 to 7 percent vinyl bromide and a second component consisting of at least 80 percent acrylonitrile, up to 15 percent vinyl acetate and 1 to 7 percent vinyl bromide.
 6. The process of claim 1 wherein the composite fiber is a bicomponent fiber consisting of a synthetic polymeric component consisting of a copolymer of from 85 to 95 percent acrylonitrile and from 5 to 15 percent vinyl acetate and a second polymeric component consisting of a terpolymer of 80 to 95 percent acrylonitrile, 5 to 15 percent vinyl acetate and 0.1 to 5 percent of a copolymerizable sulfonate with a difference of from 0.5 to 5 percent vinyl acetate in the two components.
 7. The process of claim 1 wherein the stretching is done in an atmosphere of boiling water.
 8. The process of claim 1 wherein the stretching is from 15 to 350 percent. 